Air gap and air spacer pinch off

ABSTRACT

Embodiments are directed to a method of forming a semiconductor device and resulting structures having an air spacer between a gate and a contact by forming a gate on a substrate and over a channel region of a semiconductor fin. A contact is formed on a doped region of the substrate such that a space between the contact and the gate defines a trench. A first dielectric layer is formed over the gate and the contact such that the first dielectric layer partially fills the trench. A second dielectric layer is formed over the first dielectric layer such that an air spacer forms in the trench between the gate and the contact.

DOMESTIC AND/OR FOREIGN PRIORITY

This application is a continuation of U.S. application Ser. No.15/280,457, titled “AIR GAP AND AIR SPACER PINCH OFF” filed Sep. 29,2016, the entire contents of which are incorporated herein by reference.

BACKGROUND

The present invention relates in general to semiconductor devicefabrication methods and resulting structures. More specifically, thepresent invention relates to fabrication methods and resultingstructures for a semiconductor device having an air spacer between agate and a contact. The present invention also relates to fabricationmethods and resulting structures for a semiconductor device having anair gap between metal interconnect layers.

In contemporary semiconductor device fabrication processes, a largenumber of semiconductor devices, such as field effect transistors(FETs), are fabricated on a single wafer. Some non-planar transistordevice architectures, such as vertical field effect transistors (VFETs),employ semiconductor fins and side-gates that can be contacted outsidethe active region, resulting in increased device density and performanceover lateral devices. In contemporary VFET devices, in contrast toconventional FETs, the source to drain current flows through a verticalpillar in a direction that is perpendicular with respect to a horizontalmajor surface of the wafer or substrate. A VFET can achieve a smallerdevice footprint because its channel length is decoupled from thecontacted gate pitch. Unfortunately, as device dimensions and componentspacing shrink, parasitic capacitance tends to increase. Parasiticcapacitance, or conductor-to-conductor capacitance, between twoconductors is a function of the length and thickness of the conductors,as well as the distance separating the conductors.

SUMMARY

According to embodiments of the present invention, a method offabricating a semiconductor device having an air spacer between a gateand a contact is provided. The method can include forming a gate on asubstrate, wherein the gate is also formed over a channel region of asemiconductor fin. A contact is formed on a doped region of thesubstrate, and a space between the contact and the gate defines atrench. A first dielectric layer is formed over the gate and thecontact, and the first dielectric layer partially fills the trench. Asecond dielectric layer is formed over the first dielectric layer suchthat an air spacer is formed in the trench between the gate and thecontact.

According to embodiments of the present invention, a method offabricating a semiconductor device having an air spacer between a gateand a contact is provided. The method can include forming a gate on asubstrate, wherein the gate is also formed over a channel region of asemiconductor fin. A hard mask is formed over a surface of the gate, anda contact is formed on a doped region of the substrate such that thecontact is adjacent to the gate. A spacer is formed between the gate andthe contact. The hard mask and a portion of the spacer are removed toform a trench between the gate and the contact, and the remainingportion of the spacer partially fills the trench. An interlayerdielectric is formed over the spacer such that an air spacer is formedin the trench between the gate and the contact.

According to embodiments of the present invention, a structure having anair spacer between a gate and a contact is provided. The structure caninclude a gate disposed above a substrate, wherein the gate is alsoformed over a channel region of a semiconductor fin. A contact is formedon a doped region of the substrate such that a space between the contactand the gate define a trench. A first dielectric layer partially fillsthe trench, and a second dielectric layer is formed over the firstdielectric layer and the trench. An air spacer is trapped between thegate and the contact, wherein the air spacer is formed in the trenchbetween the first and second dielectric layers.

According to embodiments of the present invention, a method offabricating a semiconductor device having an air gap between metalinterconnect layers is provided. The method can include forming a firstand a second contact in a first dielectric layer such that the firstcontact is adjacent to the second contact. A first cap is formed on asurface of the first contact and a second cap is formed on a surface ofthe second contact. A portion of the first dielectric layer is removedto expose sidewalls of the first and second contacts such that a spacebetween the first and second contacts defines a trench. A barrier lineris formed over the first and second contacts, the first and second caps,and the first dielectric layer such that the barrier liner partiallyfills the trench. A second dielectric layer is formed over the barrierliner such that an air gap forms in the trench.

According to embodiments of the present invention, a method offabricating a semiconductor device having an air gap between metalinterconnect layers is provided. The method can include forming a trenchin a first dielectric layer and forming a first liner including a firstmaterial on the first dielectric layer such that the first linerpartially fills the trench. A second liner including a second materialis formed on the first liner. A contact is formed in the trench suchthat the second liner is between the contact and the first dielectriclayer. A self-forming third liner including a third material is formedby diffusing a portion of the second material through the first liner.

According to embodiments of the present invention, a structure having anair gap between metal interconnect layers is provided. The structure caninclude a first and a second contact formed in a first dielectric layersuch that the first contact is adjacent to the second contact. A firstcap is formed on a surface of the first contact and a second cap isformed on a surface of the second contact. The structure includes abarrier liner formed over the first and second contacts, the first andsecond caps, and the first dielectric layer, such that the barrier linerpartially fills a trench between the first and second contacts. A seconddielectric layer is formed over the barrier liner such that a trappedair gap is formed in the trench.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter of the present invention is particularly pointed outand distinctly defined in the claims at the conclusion of thespecification. The foregoing and other features and advantages areapparent from the following detailed description taken in conjunctionwith the accompanying drawings in which:

FIG. 1 depicts a cross-sectional view of a structure having gates formedon a substrate during an intermediate operation of a method offabricating a semiconductor device according to one or more embodimentsof the present invention;

FIG. 2 depicts a cross-sectional view of the structure after removingcaps and portions of an interlayer dielectric (ILD) to expose sidewallsof each gate according to one or more embodiments of the presentinvention;

FIG. 3 depicts a cross-sectional view of the structure after forming afirst dielectric layer over the gates and the remaining portions of theILD according to one or more embodiments of the present invention;

FIG. 4 depicts a cross-sectional view of the structure after forming asecond dielectric layer over the first dielectric layer according to oneor more embodiments of the present invention;

FIG. 5 depicts a cross-sectional view of a structure having a gateformed on a substrate during an intermediate operation of a method offabricating a semiconductor device according to one or more embodimentsof the present invention;

FIG. 6 depicts a cross-sectional view of a structure having a contactbetween a first gate and a second gate during an intermediate operationof a method of fabricating a semiconductor device according to one ormore embodiments of the present invention;

FIG. 7 depicts a cross-sectional view of a structure having a firstcontact and a second contact formed in a first dielectric layer duringan intermediate operation of a method of fabricating a semiconductordevice according to one or more embodiments of the present invention;

FIG. 8 depicts a cross-sectional view of the structure after removingportions of the first dielectric layer to expose sidewalls of the firstand second contacts according to one or more embodiments of the presentinvention;

FIG. 9 depicts a cross-sectional view of the structure after forming abarrier liner over the contacts, the first and second caps, and thefirst dielectric layer according to one or more embodiments of thepresent invention;

FIG. 10 depicts a cross-sectional view of the structure after forming adielectric layer over portions of the barrier liner, trapping a pocketof air in the trench between the contacts according to one or moreembodiments of the present invention;

FIG. 11 depicts a cross-sectional view of a structure having an air gapformed between a first contact and a second contact during anintermediate operation of a method of fabricating a semiconductor deviceaccording to one or more embodiments of the present invention;

FIG. 12 depicts a cross-sectional view of a structure after forming atrench in a first dielectric layer during an intermediate operation of amethod of fabricating a semiconductor device according to one or moreembodiments of the present invention;

FIG. 13 depicts a cross-sectional view of the structure after forming acontact in the trench according to one or more embodiments of thepresent invention;

FIG. 14 depicts a cross-sectional view of the structure afterplanarizing a surface of the contact selective to the first dielectriclayer to remove overburden according to one or more embodiments of thepresent invention; and

FIG. 15 depicts a cross-sectional view of the structure after forming acap on a surface of the contact according to one or more embodiments ofthe present invention.

DETAILED DESCRIPTION

Various embodiments of the present invention are described herein withreference to the related drawings. Alternative embodiments can bedevised without departing from the scope of this invention. It is notedthat various connections and positional relationships (e.g., over,below, adjacent, etc.) are set forth between elements in the followingdescription and in the drawings. These connections and/or positionalrelationships, unless specified otherwise, can be direct or indirect,and the present invention is not intended to be limiting in thisrespect. Accordingly, a coupling of entities can refer to either adirect or an indirect coupling, and a positional relationship betweenentities can be a direct or indirect positional relationship. As anexample of an indirect positional relationship, references in thepresent description to forming layer “A” over layer “B” includesituations in which one or more intermediate layers (e.g., layer “C”) isbetween layer “A” and layer “B” as long as the relevant characteristicsand functionalities of layer “A” and layer “B” are not substantiallychanged by the intermediate layer(s).

The following definitions and abbreviations are to be used for theinterpretation of the claims and the specification. As used herein, theterms “comprises,” “comprising,” “includes,” “including,” “has,”“having,” “contains” or “containing,” or any other variation thereof,are intended to cover a non-exclusive inclusion. For example, acomposition, a mixture, process, method, article, or apparatus thatcomprises a list of elements is not necessarily limited to only thoseelements but can include other elements not expressly listed or inherentto such composition, mixture, process, method, article, or apparatus.

Additionally, the term “exemplary” is used herein to mean “serving as anexample, instance or illustration.” Any embodiment or design describedherein as “exemplary” is not necessarily to be construed as preferred oradvantageous over other embodiments or designs. The terms “at least one”and “one or more” are understood to include any integer number greaterthan or equal to one, i.e. one, two, three, four, etc. The terms “aplurality” are understood to include any integer number greater than orequal to two, i.e. two, three, four, five, etc. The term “connection”can include an indirect “connection” and a direct “connection.”

References in the specification to “one embodiment,” “an embodiment,”“an example embodiment,” etc., indicate that the embodiment describedcan include a particular feature, structure, or characteristic, butevery embodiment may or may not include the particular feature,structure, or characteristic. Moreover, such phrases are not necessarilyreferring to the same embodiment. Further, when a particular feature,structure, or characteristic is described in connection with anembodiment, it is submitted that it is within the knowledge of oneskilled in the art to affect such feature, structure, or characteristicin connection with other embodiments whether or not explicitlydescribed.

For purposes of the description hereinafter, the terms “upper,” “lower,”“right,” “left,” “vertical,” “horizontal,” “top,” “bottom,” andderivatives thereof shall relate to the described structures andmethods, as oriented in the drawing figures. The terms “overlying,”“atop,” “on top,” “positioned on” or “positioned atop” mean that a firstelement, such as a first structure, is present on a second element, suchas a second structure, wherein intervening elements such as an interfacestructure can be present between the first element and the secondelement. The term “direct contact” means that a first element, such as afirst structure, and a second element, such as a second structure, areconnected without any intermediary conducting, insulating orsemiconductor layers at the interface of the two elements. It should benoted, the term “selective to,” such as, for example, “a first elementselective to a second element,” means that a first element can be etchedand the second element can act as an etch stop.

For the sake of brevity, conventional techniques related tosemiconductor device and integrated circuit (IC) fabrication may or maynot be described in detail herein. Moreover, the various tasks andprocess steps described herein can be incorporated into a morecomprehensive procedure or process having additional steps orfunctionality not described in detail herein. In particular, varioussteps in the manufacture of semiconductor devices andsemiconductor-based ICs are well known and so, in the interest ofbrevity, many conventional steps will only be mentioned briefly hereinor will be omitted entirely without providing the well-known processdetails.

By way of background, however, a more general description of thesemiconductor device fabrication processes that can be utilized inimplementing one or more embodiments of the present invention will nowbe provided. Although specific fabrication operations used inimplementing one or more embodiments of the present invention can beindividually known, the described combination of operations and/orresulting structures of the present invention are unique. Thus, theunique combination of the operations described according to the presentinvention utilize a variety of individually known physical and chemicalprocesses performed on a semiconductor (e.g., silicon) substrate, someof which are described in the immediately following paragraphs.

In general, the various processes used to form a micro-chip that will bepackaged into an IC fall into four general categories, namely, filmdeposition, removal/etching, semiconductor doping andpatterning/lithography. Deposition is any process that grows, coats, orotherwise transfers a material onto the wafer. Available technologiesinclude physical vapor deposition (PVD), chemical vapor deposition(CVD), plasma-enhanced chemical vapor deposition (PECVD),electrochemical deposition (ECD), molecular beam epitaxy (MBE) and morerecently, atomic layer deposition (ALD) and plasma-enhanced atomic layerdeposition (PEALD), among others.

Removal/etching is any process that removes material from the wafer.Examples include etch processes (either wet or dry), andchemical-mechanical planarization (CMP), and the like. Reactive ionetching (RIE), for example, is a type of dry etching that useschemically reactive plasma to remove a material, such as a maskedpattern of semiconductor material, by exposing the material to abombardment of ions that dislodge portions of the material from theexposed surface. The plasma is generated under low pressure (vacuum) byan electromagnetic field.

Semiconductor doping is the modification of electrical properties bydoping, for example, transistor sources and drains, generally bydiffusion and/or by ion implantation. These doping processes arefollowed by furnace annealing or by rapid thermal annealing (RTA).Annealing serves to activate the implanted dopants. Films of bothconductors (e.g., poly-silicon, aluminum, copper, etc.) and insulators(e.g., various forms of silicon dioxide, silicon nitride, etc.) are usedto connect and isolate transistors and their components. Selectivedoping of various regions of the semiconductor substrate allows theconductivity of the substrate to be changed with the application ofvoltage. By creating structures of these various components, millions oftransistors can be built and wired together to form the complexcircuitry of a modern microelectronic device.

Semiconductor lithography is the formation of three-dimensional reliefimages or patterns on the semiconductor substrate for subsequenttransfer of the pattern to the substrate. In semiconductor lithography,the patterns are formed by a light sensitive polymer called aphoto-resist. To build the complex structures that make up a transistorand the many wires that connect the millions of transistors of acircuit, lithography and etch pattern transfer steps are repeatedmultiple times. Each pattern being printed on the wafer is aligned tothe previously formed patterns and slowly the conductors, insulators andselectively doped regions are built up to form the final device.

Turning now to a more detailed description of technologies relevant tothe present invention, as previously noted herein, some non-planartransistor device architectures, such as VFETs, employ semiconductorfins and side-gates that can be contacted outside the active region,resulting in increased device density over lateral devices. However,there are challenges to providing VFETs with equal or superiorperformance characteristics to lateral devices. As the features of aVFET are reduced in size and increased in aspect ratio, parasiticcapacitance effects between features are exacerbated. For example,during front end of line (FEOL) fabrication at the sub-10 nm node, theparasitic capacitance between a gate and an adjacent contact becomessignificant. In another example, during back end of line (BEOL)fabrication at intra-level spacing below about 15 nm, parasiticcapacitance between interconnects becomes significant. Parasiticcapacitance contributes to undesired device effects such asresistive-capacitive (RC) delay, power dissipation, and cross-talk. RCdelay refers to the delay in signal speed or propagation experienced ina circuit as a function of the product of the resistance and capacitanceof the circuit components. Thus, a method and structure is desired forreducing the capacitance between a gate and an adjacent contact. Amethod and structure is also desired for reducing the intra-levelcapacitance between interconnects.

Turning now to an overview of aspects of the present invention, one ormore embodiments provide methods of fabricating a semiconductor devicehaving an air spacer between a gate and a contact. The described methodsemploy exposing a trench between the gate and the contact. A pocket ofair is trapped in the trench by pinching off the trench with adielectric. The pocket of air serves as an air spacer between the gateand the contact. In other aspects of the present invention, one or moreembodiments provide methods of fabricating a semiconductor device havingan air gap between interconnects. The described methods employ exposinga trench between adjacent contacts in a dielectric layer. A pocket ofair is trapped in the trench by pinching off the trench with adielectric. The pocket of air serves as an air gap between the contacts.Methods for forming an air spacer and an air gap and the resultingstructures therefrom in accordance with embodiments of the presentinvention are described in detail below by referring to the accompanyingdrawings in FIGS. 1-15.

FIG. 1 illustrates a cross-sectional view of a structure 100 havinggates 102A, 102B, and 102C formed on a substrate 104 during anintermediate operation of a method of fabricating a semiconductor deviceaccording to one or more embodiments. The substrate 104 can be anysuitable substrate material, such as, for example, monocrystalline Si,SiGe, SiC, III-V compound semiconductor, II-VI compound semiconductor,or semiconductor-on-insulator (SOI). For ease of discussion, referencecan be made to operations performed on and to gates 102A, 102B, 102C,and to a single gate (i.e., gate 102B) of the structure 100. It isunderstood that the structure 100 can include a plurality of gates(e.g., gates 102A, 102B, 102C, and other gates not illustrated forsimplicity).

Any known composition and manner of forming the gates 102A, 102B, and102C can be utilized. The gates 102A, 102B, and 102C (sometimes referredto as gate conductors) can be made of, for example, polycrystalline oramorphous silicon, germanium, silicon germanium, a metal (e.g.,tungsten, titanium, tantalum, ruthenium, zirconium, cobalt, copper,aluminum, lead, platinum, tin, silver, gold), a conducting metalliccompound material (e.g., tantalum nitride, titanium nitride, tantalumcarbide, titanium carbide, titanium aluminum carbide, tungsten silicide,tungsten nitride, ruthenium oxide, cobalt silicide, nickel silicide),carbon nanotube, conductive carbon, graphene, or any suitablecombination of these materials. The conductive material can furtherinclude dopants that are incorporated during or after deposition. Insome embodiments, gate 102A includes a cap 110A (sometimes referred toas a hard mask). It is understood that each gate (e.g., 102B, 102C) caninclude a cap (e.g., cap 110B, 110C).

Contacts 106A and 106B are formed on doped regions 108A and 108B of thesubstrate 104, respectively. In some embodiments, each contact (e.g.,contact 106A) is formed adjacent to a gate (e.g., 102A). In someembodiments, each contact (e.g., contact 106A) is formed between eachpair of adjacent gates (e.g., gates 102A and 102B). The doped regions108A and 108B can each be a source or drain region formed on thesubstrate 104 by a variety of methods, such as, for example, diffusion,ion implantation of a dopant into the substrate, or in-situ dopedepitaxy. The contacts 106A and 106B can be of any suitable conductingmaterial, such as, for example, a metal (e.g., tungsten, titanium,tantalum, ruthenium, zirconium, cobalt, copper, aluminum, lead,platinum, tin, silver, gold), a conducting metallic compound material(e.g., tantalum nitride, titanium nitride, tantalum carbide, titaniumcarbide, titanium aluminum carbide, tungsten silicide, tungsten nitride,ruthenium oxide, cobalt silicide, nickel silicide), carbon nanotube,conductive carbon, graphene, or any suitable combination of thesematerials. The conductive material can further include dopants that areincorporated during or after deposition. Any known manner of forming thecontacts 106A and 106B can be utilized. In some embodiments, thecontacts 106A and 106B are copper and each includes a barrier metalliner. In some embodiments, the barrier metal liner is deposited into acontact trench prior to depositing the contact (not illustrated). Thebarrier metal liner prevents the copper from diffusing into, or doping,the surrounding materials, which can degrade their properties. Silicon,for example, forms deep-level traps when doped with copper. An idealbarrier metal liner must limit copper diffusivity sufficiently tochemically isolate the copper conductor from the surrounding materialsand should have a high electrical conductivity, for example, tantalumnitride and tantalum (TaN/Ta), titanium, titanium nitride, cobalt,ruthenium, and manganese.

A first interlayer dielectric (ILD) 111 fills the space between thecontact 106A and the adjacent gates 102A and 102B. It is understood thatthe ILD 111 also fills the space between each adjacent contact and gate.Any known manner of forming the ILD 111 can be utilized. In someembodiments, the ILD 111 is deposited by a spin-on coating operation. Insome embodiments, the ILD 111 is formed as a spacer between eachadjacent gate and contact (e.g., a spacer between gate 102A and contact106A). The ILD 111 can be any suitable material, such as, for example,an oxide or carbon doped silicon oxide. In some embodiments, the ILD 111is silicon dioxide (SiO₂) or SiCOH.

FIG. 2 illustrates a cross-sectional view of the structure 100 afterremoving the caps 110A, 110B, and 110C and portions of the ILD 111 toexpose sidewalls of each gate 102A, 102B, and 102C. The space betweeneach gate (e.g., gate 102B) and contact (e.g., 106B) defines a trench(e.g., trench 202A). For ease of illustration, only trench 202A isdepicted. Remaining portions of the ILD 111 partially fill each trench.For example, remaining portion 200B partially fills the trench 202A. Anyknown manner of removing the caps 110A, 110B, and 110C and portions ofthe ILD 111 can be utilized. In some embodiments, an etch process, whichcan be a wet etch process, a dry etch process or a combination thereofis used. In some embodiments, a directional etch, such as a RIE,selective to the gate material (e.g., gate 102B material) is used toform the trench 202A.

FIG. 3 illustrates a cross-sectional view of the structure 100 afterforming a first dielectric layer 300 over the gates 102A, 102B, and102C, the contacts 106A and 106B, and the remaining portions of the ILD111 (e.g., portions 200A and 200B). The first dielectric layer 300partially fills each trench (e.g., trench 202A). Any known compositionand manner of forming the first dielectric layer 300 can be utilized. Insome embodiments, the first dielectric layer 300 is conformal.“Conformal” as used herein means that the thickness of the firstdielectric layer 300 is substantially the same on all surfaces, or thethickness variation is less than 50% of the nominal thickness. In someembodiments, the first dielectric layer 300 can be conformally formedusing CVD, PECVD, atomic layer deposition (ALD), evaporation, physicalvapor deposition (PVD), chemical solution deposition, or other likeprocesses. In some embodiments, the first dielectric layer 300 has athickness of about 2 nm to about 8 nm. In other embodiments, the firstdielectric layer 300 has a thickness of about 3 nm to about 6 nm. Instill other embodiments, the first dielectric layer 300 has a thicknessof about 3 nm. In some embodiments, the first dielectric layer 300 is asilicon nitride (SiN), Si₃N₄, SiO₂, a silicon carbonitride (SiCN), asilicoboron carbonitride (SiBCN), or a silicon oxygen carbonitride(SiOCN). In some embodiments, the first dielectric layer 300 is a metalsilicate, such as, for example, MnSiO_(x). In some embodiments, themetal silicate is a low-k dielectric having a dielectric constant lessthan about 4.0. Metal silicates, such as, for example, MnSiO_(x),advantageously serve as a copper barrier, thus obviating the need for aseparate copper barrier metal liner.

FIG. 4 illustrates a cross-sectional view of the structure 100 afterforming a second dielectric layer 400 over the first dielectric layer300. Air spacers 402A, 402B, 402C, and 402D each form in a trenchbetween a gate and a contact. For example, air spacer 402C forms intrench 202A between gate 102B and contact 106B. In some embodiments, thesecond dielectric layer 400 pinches off an opening in each trench totrap an air pocket in each trench (e.g., trench 202A). Each air pocketdefines an air spacer. Any known composition and manner of forming thesecond dielectric layer 400 can be utilized. In some embodiments, thesecond dielectric layer 400 is nonconformally formed using, for example,PECVD. In some embodiments, the second dielectric layer 400 has athickness of about 10 nm to about 110 nm. In other embodiments, thesecond dielectric layer 400 has a thickness of about 30 nm to about 90nm. In still other embodiments, the second dielectric layer 400 has athickness of about 80 nm. In some embodiments, the second dielectriclayer 400 is a nitride, a silicon nitride, Si₃N₄, SiO, SiO₂, SiCN,SiBCN, SiOCN, MnSiOx, MnSiCO_(x), or MnSiCON_(x). In some embodiments,the second dielectric layer 400 is a low-k dielectric having adielectric constant of about 3.7 to about 5.1. As air has a lowdielectric constant of about 1, the air spacers 402A, 402B, 402C, and402D serve to reduce the parasitic capacitance between each gate-contactpair. For example, air spacer 402C reduces the parasitic capacitancebetween gate 102B and contact 106A as well as the parasitic capacitancebetween gate 102B and contact 106B.

FIG. 5 illustrates a cross-sectional view of a structure 500 having agate 502 formed on a substrate 504 during an intermediate operation of amethod of fabricating a semiconductor device according to one or moreembodiments. In some embodiments, gate 502 includes a gate dielectric(e.g., high-k dielectric) region 506 defining a channel interfacebetween the gate 502 and a semiconductor fin 508. In some embodiments,the gate dielectric region 506 is formed between the gate 502 and thesemiconductor fin 508 to modify the work function of the gate 502. Thegate 502 can further include a work function metal layer (not depicted)next to the gate dielectric region 506. The work function layer can be anitride, including but not limited to titanium nitride (TiN), hafniumnitride (HfN), hafnium silicon nitride (HfSiN), tantalum nitride (TaN),tantalum silicon nitride (TaSiN), tungsten nitride (WN), molybdenumnitride (MoN), niobium nitride (NbN); a carbide, including but notlimited to titanium carbide (TiC) titanium aluminum carbide (TiAlC),tantalum carbide (TaC), hafnium carbide (HfC), and combinations thereof,during an operation for forming a VFET, according to one or moreembodiments.

The gate dielectric region 506 can be made of, for example, siliconoxide, silicon nitride, silicon oxynitride, boron nitride, high-kmaterials, or any combination of these materials. Examples of high-kmaterials include but are not limited to metal oxides such as hafniumoxide, hafnium silicon oxide, hafnium silicon oxynitride, lanthanumoxide, lanthanum aluminum oxide, zirconium oxide, zirconium siliconoxide, zirconium silicon oxynitride, tantalum oxide, titanium oxide,barium strontium titanium oxide, barium titanium oxide, strontiumtitanium oxide, yttrium oxide, aluminum oxide, lead scandium tantalumoxide, and lead zinc niobate. The high-k materials can further includedopants such as lanthanum and aluminum. In some embodiments, the gatedielectric region can have a thickness of about 0.5 nm to about 4 nm. Inother embodiments, the gate dielectric region can have a thickness ofabout 2 nm to about 3 nm.

In some embodiments, the gate 502 is formed between a bottom spacer 510and a top spacer 512. In some embodiments, the bottom spacer 510 isformed on a doped region 514 of the substrate 504. The bottom spacer 510and the top spacer 512 can be any suitable material, such as, forexample, a low-k dielectric, a nitride, silicon nitride, SiOCN, SiBCN,MnSiOx, MnSiCO_(x), or MnSiCON_(x). In some embodiments, the bottomspacer 510 and the top spacer 512 are different materials.

The semiconductor fin 508 can be formed on the doped region 514 usingknown semiconductor fabrication techniques. For example, in someembodiments, a patterned hard mask (not illustrated) is etched to exposeportions of the substrate 504. The exposed portions of the substrate 504can be removed to form a plurality of semiconductor fins, including,e.g., semiconductor fin 508. The patterned hard mask is then removedusing an etch process, which can be a wet etch process, a dry etchprocess or a combination thereof. The semiconductor fin 508 can be anysuitable material, such as, for example, Si, SiGe, Group III-V channelmaterial, or other suitable channel materials. Group III-V channelmaterials include materials having at least one group III element and atleast one group V element, such as, for example, one or more of aluminumgallium arsenide, aluminum gallium nitride, aluminum arsenide, aluminumindium arsenide, aluminum nitride, gallium antimonide, gallium aluminumantimonide, gallium arsenide, gallium arsenide antimonide, galliumnitride, indium antimonide, indium arsenide, indium gallium arsenide,indium gallium arsenide phosphide, indium gallium nitride, indiumnitride, indium phosphide and alloy combinations including at least oneof the foregoing materials. The hard mask can be any suitable material,such as, for example, a nitride or silicon nitride. In some embodiments,a plurality of semiconductor fins is formed on the bottom doped region514. In some embodiments, the fin pitch, or spacing, between eachsemiconductor fin can be about 20 nm to about 100 nm. In otherembodiments, the fin pitch is about 30 nm to about 50 nm.

A contact 516 is formed on the doped region 514 of the substrate 504.The contact 516 can be of any suitable conducting material formed in alike manner as the contacts 106A and 106B (as depicted in FIG. 1). Thecontact 516 can be, for example, a metal (e.g., tungsten, titanium,tantalum, ruthenium, zirconium, cobalt, copper, aluminum, lead,platinum, tin, silver, gold), a conducting metallic compound material(e.g., tantalum nitride, titanium nitride, tantalum carbide, titaniumcarbide, titanium aluminum carbide, tungsten silicide, tungsten nitride,ruthenium oxide, cobalt silicide, nickel silicide), carbon nanotube,conductive carbon, graphene, or any suitable combination of thesematerials. The conductive material can further include dopants that areincorporated during or after deposition.

An air spacer 518 is formed between the contact 516 and the gate 502according to one or more embodiments. The air spacer 518 serves toreduce the parasitic capacitance between the gate 502 and the contact516. In some embodiments, the air spacer 518 is trapped between a firstdielectric layer 520 and a second dielectric layer 522 (also referred toas an interlayer dielectric) according to one or more embodiments.

In some embodiments, a top epitaxy region 524 is formed on a portion ofthe semiconductor fin 508. Any known manner of forming the top epitaxyregion 524 can be utilized. In some embodiments, epitaxial growth, CVD,ECD, MBE, or ALD is employed to form the top epitaxy region 524. In someembodiments, the top epitaxy region 524 is in-situ doped. In someembodiments, the top epitaxy region 524 is formed using ultrahigh vacuumchemical vapor deposition (UHVCVD), rapid thermal chemical vapordeposition (RTCVD), metalorganic chemical vapor deposition (MOCVD),low-pressure chemical vapor deposition (LPCVD), limited reactionprocessing CVD (LRPCVD), or molecular beam epitaxy (MBE). Epitaxialmaterials can be grown from gaseous or liquid precursors. Epitaxialmaterials can be grown using vapor-phase epitaxy (VPE), molecular-beamepitaxy (MBE), liquid-phase epitaxy (LPE), or other suitable process.Epitaxial silicon, silicon germanium (SiGe), and/or carbon doped silicon(Si:C) silicon can be doped during deposition (in-situ doped) by addingdopants, n-type dopants (e.g., phosphorus or arsenic) or p-type dopants(e.g., boron or gallium), depending on the type of transistor. Thedopant concentration in the source/drain can range from 1×10¹⁹ cm-3 to2×10²¹ cm⁻³, or preferably between 2×10²⁰ cm⁻³ to 1×10²¹ cm⁻³.

In some embodiments, a gate contact 526 is formed on the top epitaxyregion 524, above the gate 502. Any known manner of forming the gatecontact 526 can be utilized. In some embodiments, the gate contact 526can be copper. In some embodiments, the first dielectric layer 520 is aconformal metal silicate liner formed over the gate contact 526, thegate 502, and the contact 516. The first dielectric layer 520 can be,for example, MnSiO_(x), MnSiCO_(x), or MnSiCON_(x). The metal silicateliner serves as a copper barrier, thus obviating the need for a separatecopper barrier metal liner, according to one or more embodiments.

FIG. 6 illustrates a cross-sectional view of a structure 600 having acontact 602 between a first gate 604 and a second gate 606 during anintermediate operation of a method of fabricating a semiconductor deviceaccording to one or more embodiments. The contact 602 is formed on adoped region 608. Air spacer 610 is formed between the contact 602 andthe first gate 604 according to one or more embodiments. Air spacer 612is formed between the contact 602 and the second gate 606 according toone or more embodiments.

FIG. 7 illustrates a cross-sectional view of a structure 700 having afirst contact 702 and a second contact 704 formed in a first dielectriclayer 706, during an intermediate operation of a method of fabricating asemiconductor device according to one or more embodiments. The firstcontact 702 is adjacent to the second contact 704. Any known compositionand manner of forming the contacts 702 and 704 can be utilized. In someembodiments, the contacts 702 and 702 are made of, for example, copper.The first dielectric layer 702 can be any known dielectric material,such as, for example, an oxide.

In some embodiments, a cap 708 is formed on the first contact 702. A cap710 is similarly formed on the second contact 704. The caps 708 and 710can be of any suitable conducting material, such as, for example, ametal (e.g., Cobalt, tungsten, titanium, tantalum, ruthenium, zirconium,cobalt, copper, aluminum, lead, platinum, tin, silver, gold), aconducting metallic compound material (e.g., tantalum nitride, titaniumnitride, tantalum carbide, titanium carbide, titanium aluminum carbide,tungsten silicide, tungsten nitride, ruthenium oxide, cobalt silicide,nickel silicide), carbon nanotube, conductive carbon, graphene, or anysuitable combination of these materials. The conductive material canfurther include dopants that are incorporated during or afterdeposition.

In some embodiments, an inner liner 112 is formed between the firstcontact 702 and the first dielectric layer 706, and an inner liner 114is formed between the second contact 704 and the first dielectric layer706. The inner liners 112 and 114 can serve as both a diffusion barrier(also known as a barrier metal liner) and as an adhesion promotinglayer, according to one or more embodiments. The inner liners 112 and114 can be of any suitable material, such as, for example, tantalumnitride (TaN), cobalt, or ruthenium.

FIG. 8 illustrates a cross-sectional view of the structure 700 afterremoving portions of the first dielectric layer 706 to expose sidewallsof the first and second contacts 702 and 704. Any known manner ofremoving portions of the first dielectric layer 706 can be utilized. Insome embodiments, an etch process, which can be a wet etch process, adry etch process or a combination thereof is used. In some embodiments,the first dielectric layer 706 is exposed to plasma to create damage anda wet etch selectively removes the damaged dielectric material. Removingportions of the first dielectric layer 706 forms a trench 800 betweenthe first contact 702 and the second contact 704. In some embodiments,the trench 800 has an aspect ratio of greater than about 1.3. In someembodiments, the trench 800 has an aspect ratio of greater than about1.5.

FIG. 9 illustrates a cross-sectional view of the structure 700 afterforming a barrier liner 900 over the contacts 702 and 704, the first andsecond caps 708 and 710, and the first dielectric layer 706. The barrierliner 900 partially fills the trench 800. The barrier liner 900 can beof any suitable material. In some embodiments, the barrier liner 900 isa metal silicate, such as, for example, MnSiO_(x), MnSiCO_(x), andMnSiCNO. In some embodiments, the metal silicate barrier liner 900 isdirectly deposited using, for example, PEALD or PECVD. As describedpreviously herein, a thick copper barrier metal liner is typicallyrequired around copper contacts to prevent copper diffusion into thesurrounding materials. As these metal silicates serve as a copperbarrier, the copper barrier metal liner can be significantly reduced inthickness or removed entirely.

FIG. 10 illustrates a cross-sectional view of the structure 700 afterforming a dielectric layer 1000 over portions of the barrier liner 900,trapping a pocket of air 1002 (also referred to as an air gap) in thetrench 800 between the contacts 702 and 704. In some embodiments, thedielectric layer 1000 is nonconformally deposited to pinch off anopening of the trench 800. As air has a low dielectric constant of about1, the air gap 1002 reduces the parasitic capacitance between thecontacts 702 and 704.

In some embodiments, portions 1004 and 1006 of the barrier liner 900 areself-forming layers which are not directly deposited. Instead, anintermediate film (e.g., barrier liner 900) including a first materialis conformally deposited over the first and second contacts 702 and 704,the film partially filling the trench 800. The first material can be,for example, Mn or MnN_(y). A dielectric layer 1000 including a secondmaterial is formed on portions of the film. The second material can beany suitable dielectric material, such as, for example, a low-kdielectric, SiO_(x), SiCO_(x), SiCNO, and porous SiCOH. A thermal or UVbased annealing process self-forms the portions 1004 and 1006 of thebarrier liner 900 by causing the contacting portions of the firstmaterial and the second material to react. The final composition of theportions 1004 and 1006 of the barrier liner 900 depends upon thecomposition of the film and the dielectric layer 1000. In someembodiments, the portions 1004 and 1006 are self-formed metal silicates,such as, for example, MnSiO_(x), MnSiCO_(x), and MnSiCNO. For example,if the film is Mn and the dielectric layer 1000 is SiO_(x), then theannealing process will generate a self-forming MnSiO_(x) barrier liner900. In another example, if the film is MnN_(y) and the dielectric layer1000 is SiCNO, then the annealing process will generate a self-formingMnN_(y)SiCNO barrier liner 900. For clarity, only portions 1004 and 1006are depicted. It is understood that all portions of the barrier liner900 in contact with portions of the first or second dielectric layers706 and 1000 self-form in a similar manner during the annealing process.

FIG. 11 illustrates a cross-sectional view of a structure 1100 having anair gap 1102 formed between a first contact 1104 and a second contact1106 during an intermediate operation of a method of fabricating asemiconductor device according to one or more embodiments. A metalsilicate conformal liner 1108 is formed over the contacts 1104 and 1106,according to one or more embodiments. A nonconformal interlayerdielectric 1110 is formed to trap the air gap 1102, according to one ormore embodiments. For clarity, only operations regarding air gap 1102are depicted. It is understood that a plurality of air gaps are formedin this manner.

FIG. 12 illustrates a cross-sectional view of a structure 1200 afterforming a trench 1202 in a first dielectric layer 1204 during anintermediate operation of a method of fabricating a semiconductor deviceaccording to one or more embodiments. Any known manner of forming thetrench 1202 can be utilized. In some embodiments, an etch process, whichcan be a wet etch process, a dry etch process or a combination thereofis used to remove portions of the first dielectric layer 1204.

A metal barrier liner 1206 is formed between a first liner 1208 and thefirst dielectric layer 1204, according to one or more embodiments. Themetal barrier liner 1206 serves as an adhesion layer for the first liner1208 and can be, for example, TaN. The metal barrier liner 1206partially fills the trench 1202. The first liner 1208 can be of anysuitable material, such as, for example, cobalt. The first liner 1208can be conformally formed on the metal barrier liner 1206 using CVD,PECVD, ALD, PVD, chemical solution deposition, or other like processes.

A second liner 1210 is formed on the first liner 1208. In someembodiments, the second liner 1210 is conformal. The second liner 1210can be of any suitable material, such as, for example, manganese. Thesecond liner 1212 can be conformally formed on the first liner 1208using CVD, PECVD, ALD, PVD, chemical solution deposition, or other likeprocesses.

FIG. 13 illustrates a cross-sectional view of the structure 1200 afterforming a contact 1300 in the trench 1202. In some embodiments, thecontact 1300 is deposited to overfill the trench 1202, forming anoverburden above a surface of the second liner 1210. In someembodiments, the contact 1300 is copper formed using known copperelectroplating processes followed by known post-plating annealingprocesses.

FIG. 14 illustrates a cross-sectional view of the structure 1200 afterplanarizing a surface of the contact 1300 selective to the firstdielectric layer 1204 to remove the overburden. The contact 1300 can beplanarized using any known process, such as, for example, CMP.

FIG. 15 illustrates a cross-sectional view of the structure 1200 afterforming a cap 1500 on a surface of the contact 1300 according to one ormore embodiments. The cap can be of any suitable material, such as, forexample, SiNC, SiCNO, SiNx, SiNO, or SiC. A self-forming layer 1502(also referred to as a third liner) is formed by diffusion of a materialof the second liner 1210 across the first liner 1208. The diffusedmaterial of the second liner 1210 reacts with the metal barrier liner1206 to form a third material (i.e., the material of self-forming layer1502). The final composition of the self-forming layer 1502 depends uponthe composition of the metal barrier liner 1206, the first liner 1208,and the second liner 1210. In some embodiments, the self-forming layer1502 is a metal silicate, such as, for example, TaMn_(x)O_(y),TaMnSiO_(x), TaMnSiCO_(x), TaMnSiCNO, MnSiO_(x), MnSiCO_(x), andMnSiCNO. For example, if the metal barrier liner 1206 is TaN, the firstliner 1208 is cobalt, and the second liner 1210 is manganese, themanganese will diffuse across the first liner 1208 and react with theTaN in the metal barrier liner 1206 to form TaMn_(x)O_(y).

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments described. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the invention.The terminology used herein was chosen to best explain the principles ofthe embodiment, the practical application or technical improvement overtechnologies found in the marketplace, or to enable others of ordinaryskill in the art to understand the embodiments described herein.

What is claimed is:
 1. A semiconductor device comprising: a gateelectrode disposed above a substrate and over a channel region of asemiconductor fin; a contact formed on a doped region of the substratein a manner that leaves a space between the contact and the gateelectrode defining a trench, wherein the doped region and the gateelectrode extend upward from the substrate from a same plane; a firstdielectric layer partially filling the trench; a second dielectric layerformed over the first dielectric layer and the trench; and an air spacerbetween the gate electrode and the contact and in the trench between thefirst and second dielectric layers.
 2. The semiconductor device of claim1, wherein the first dielectric layer is a conformal layer formed overthe gate electrode, the contact, and remaining portions of the spacer.3. The semiconductor device of claim 1, wherein the first dielectriclayer comprises MnSiOx, MnSiCOx, or MnSiCONx.
 4. The semiconductordevice of claim 3, wherein the first dielectric layer comprises athickness of about 2 nm to about 8 nm.
 5. The semiconductor device ofclaim 1, wherein the first dielectric layer comprises a thickness ofabout 3 nm to about 6 nm.
 6. The semiconductor device of claim 1,wherein the second dielectric layer is a nonconformal layer formed overthe trench to pinch off an opening of the trench.
 7. The semiconductordevice of claim 1, wherein the second dielectric layer comprises a low-kdielectric, a nitride, a silicon nitride (SiN), a silicon carbonitride(SiCN), a silicon oxygen carbonitride (SiOCN), or a silicoboroncarbonitride (SiBCN).
 8. The semiconductor device of claim 1, furthercomprising a plurality of adjacent gate electrodes on the substrate,each gate electrode of the plurality of adjacent gate electrodes formedover a respective channel region of a respective semiconductor fin. 9.The semiconductor device of claim 8, further comprising a respectivecontact between each pair of adjacent gate electrodes of the pluralityof adjacent gate electrodes, each respective contact formed on arespective doped region of the substrate, each respective contactseparated from a first gate electrode by a first space and a second gateelectrode by a second space, the first space defining a first trench andthe second space defining a second trench.
 10. The semiconductor deviceof claim 9, further comprising respective air spacer formed in eachrespective trench between the first and second dielectric layers.
 11. Asemiconductor device comprising: a gate electrode disposed above asubstrate and over a channel region of a semiconductor fin; a contactformed on a source or drain region of the substrate in a manner thatleaves a space between the contact and the gate electrode defining atrench, wherein the source or drain region and the gate electrode extendupward from the substrate from a same plane; a conformal dielectriclayer partially filling the trench and formed over the gate electrodeand the contact; a nonconformal dielectric layer formed over theconformal dielectric layer and the trench; and an air spacer between thegate electrode and the contact and in the trench between the conformaldielectric layer and the nonconformal dielectric layer.
 12. Thesemiconductor device of claim 11, wherein the conformal dielectric layeris deposited to a thickness of about 2 nm to about 8 nm.
 13. Thesemiconductor device of claim 11, wherein the conformal dielectric layeris deposited to a thickness of about 3 nm to about 6 nm.
 14. Thesemiconductor device of claim 11, wherein the conformal dielectric layercomprises MnSiOx, MnSiCOx, or MnSiCONx.
 15. The semiconductor device ofclaim 11, wherein the nonconformal dielectric layer pinches off anopening of the trench.
 16. The semiconductor device of claim 11, whereinthe nonconformal dielectric layer comprises a low-k dielectric, anitride, a silicon nitride (SiN), a silicon carbonitride (SiCN), asilicon oxygen carbonitride (SiOCN), or a silicoboron carbonitride(SiBCN).
 17. The semiconductor device of claim 11, further comprising aplurality of adjacent gate electrodes on the substrate, each gateelectrode of the plurality of adjacent gate electrodes formed over arespective channel region of a respective semiconductor fin.
 18. Thesemiconductor device of claim 17, further comprising a respectivecontact between each pair of adjacent gate electrodes of the pluralityof adjacent gate electrodes, each respective contact formed on arespective source or drain region of the substrate, each respectivecontact separated from a first gate electrode by a first trench and asecond gate electrode by a second trench.
 19. The semiconductor deviceof claim 18, further comprising respective air spacer formed in eachrespective trench between the conformal and nonconformal dielectriclayers.